The present invention relates to a method of fabricating electroluminescent devices and more specifically to a method of fabricating electroluminescent devices having improved resistance to degradation of light emission.
In the field of III-V compound P-N junction electroluminescent devices a problem that has existed is gradual degradation. Degradation is an electroluminescent device is when the generated light output is reduced as a function of time at a given current drive. This reduction in light output occurs in the course of device operation without any evidence of mechanical damage.
Electroluminescent devices can be of two types; when the electroluminescent radiation is incoherent, the diode source is described as a light-emitting diode, and when the radiation is coherent, the source is described as a laser.
The phenomenon of gradual degradation is a superlinear function of the current density of operation and results from the formation of nonradiative centers in the recombination region. One possibility for the formation of these nonradiative centers is clustering of point defects in the recombination region. That is to say, for gradual degradation to proceed, there must be present dislocation multiplication or impurity diffusion. For these phenomena to take place, there must be a substantial number of point defects present in the crystal. Among the most important of these defects are vacancies, for a large number of vacancies can account for movements of dislocations and impurities during operation. Therefore, a method by which electroluminescent devices can be fabricated having a lesser number of vacancies would be most desirable for the reduction of gradual degradation.